The present invention relates to a vibration-resistant impact valve with a replaceable, breakable top valve assembly. More particularly, the invention relates to such an impact valve for a gasoline vapor recovery pipeline or for a gasoline supply pipeline, but for suction systems or self-contained (own motor) systems only (not for pressurized systems).
To minimize fire and explosion hazards for gasoline dispensers and pipelines associated with such dispensers, the gasoline supply pipeline is typically provided with an impact valve near the gasoline dispenser. Such an impact valve is normally open, but will block the gasoline product line in response to sufficient impact with the gasoline dispenser. Until now, no such valve has been used on, or available for, gasoline vapor recovery lines. Such lines also create a risk of fire or explosion if broken. However, because impact valves are normally quite complicated in structure, difficult to replace, expensive, and would not create an airtight seal, and because no one is known to have put such a valve on the vapor recovery line, there have been no such valves for a vapor recovery line. Moreover, the valves are constructed so that upon sufficient impact to cause them to operate, they often will also become broken. Accordingly, they must be replaced. It is commonplace to make these valves relatively strong, but if there is a collision with the gasoline dispenser, the pipeline connected to the valve can also break. In addition, the valves are too sensitive in that they can be set off by a vibration or a minor earthquake or other disturbance, even if the pipeline does not break. In such a case, gasoline or vapor cannot be properly vented and may create a serious hazard or cause the dispenser to shut down without a clue as to the problem. These are problems for both existing valves on gasoline supply lines and for any valve, if it were to be used in a vapor recovery line. Accordingly, it is desirable to have a simple, inexpensive, easily replaceable impact valve which will localize the damage from impact, as well as reliably remain open and reliably seal the gasoline pipeline or gasoline vapor line in the event of impact.